1. Technical Field
This invention relates to a self-contained hydrating system for isolating at least one hydrating liquid and for releasing the hydrating liquid when desired. In particular, the invention relates to a self-contained hydrating system usable, for example, to isolate hydrating liquids from an iontophoresis bioelectrode and, when desired, to deliver the hydrating liquids to the iontophoresis bioelectrode.
2. Background Information
Numerous devices require fluid components or fluid communication between components for proper operation. Depending on the type of fluids or for safety, stability or storage purposes, it may be desirable to maintain fluids in a safely isolated but releasable form, e.g., an acid solution for use in a battery. There are also situations where a reaction between a fluid component and another component is important to the operation of a device but it is desirable to control when the reaction occurs. A volatile liquid, such as, for example, a smelling salt solution, may be desired to be maintained in isolation from the environment yet be readily releasable when needed. A self-contained hydrating system for isolating a hydrating liquid and for releasing the hydrating liquid when desired would be useful for purposes such as these.
A particular device requiring hydration for proper operation is an iontophoresis bioelectrode device. Iontophoretic delivery of medicaments is a useful and non-invasive technique having a number of different diagnostic and therapeutic applications. Typically, systems for iontophoretic delivery of medicaments use two conductive elements, one positive and one negative, each placed in electrical contact with a portion of the skin or a mucosal surface of the body. Also typical is that each bioelectrode contains an electrolyte solution at least one of which contains ionized medicament. An electrical power source, such as a battery is connected to the electrodes to complete the electrical circuit through the body. The charge of the ionized solution determines bioelectrode polarity such that, when current is supplied, the medicarnent ions migrate away from the electrode and are thereby delivered through the skin or mucosal surface of the patient.
Because of storage and solution stability concerns, it is desirable to be able to hydrate the bioelectrode system just prior to use. Some type of enclosure or other fluid-holding means is typically used to contain the ionized electrolyte or medicament solutions and a mechanism or structure on the enclosure is necessary to permit the introduction of solution thereunto. Such structure has typically included some type of orifice containing a plug into which a hypodermic needle or syringe cannula may be inserted to allow delivery of the solution through the orifice into the interior of the enclosure, while preventing the outflow of the solution after it has been introduced into the enclosure. The requirement of such solution receiving mechanism or enclosure increases the cost of the bioelectrode system and gives rise to potential spillage and leakage of solution. Such spillage and leakage can result in an inoperative or defective device.
Bioelectrode systems containing initially dry, but hydratable, solution-holding components and an isolated hydrating liquid which can be released to hydrate the dry components have been developed. See, e.g., Haak et al., U.S. Pat. No. 5,288,289 ("Haak") and Gyory et al., published international patent WO 93/24177 ("Gyory"), the disclosures of which are both incorporated herein by reference. For example, Haak discloses a bioelectrode system comprising breakable capsules filled with the desired hydrating liquid positioned within the material of the hydratable solution-holding components. Squeezing or flexing of the hydrating liquid-storage component breaks the capsules within to release the hydrating liquid. The hydrating liquid flows onto the electrical current distribution element and through preformed passageways to the hydratable solution-holding component. Optional wicking material is described to enhance rapid transfer of the liquid across the electrode conductor surface where the liquid can flow through the passageways to the hydratable solution-holding component.
It can be seen that the hydrating rate, the completeness of the fluid transfer, and the fluid distribution pattern is affected by the characteristics and properties of the separate elements which must be in fluid communication, i.e., the interposed electrical current distribution element material, the hydrating liquid-storage component material, the hydratable solution-holding component material, and the optional wicking material. Other variables include the size, shape, and other characteristics of the flow through openings between the hydrating liquid-storage component and the hydratable solution-holding component, the distributional arrangement of the capsules within the hydrating liquid-storage component material, and even whether or not all of the capsules break or whether the encapsulized liquid is completely dispensed from the broken capsules. Moreover, inadvertent squeezing or flexing of the hydrating liquid-storage component could occur during manufacture, shipping, storing or handling of the device. Such an occurrence could break some or all of the hydrating liquid-filled capsules and cause premature hydration of the hydratable solution-holding component. Such premature hydration could result in an unusable or defective device.
Haak also discloses a bioelectrode system wherein the hydrating liquid-storage component and the hydratable solution-holding component are attached to a first portion of the system while a second portion of the system contains pins for puncturing the hydrating liquid-storage component. In this embodiment, manual alignment and assembly of the first and second portions causes the pins to puncture the hydrating liquid-storage component and thereby release the fluid to hydrate the hydratable solution-holding component. In another embodiment, the system portions are not separate from each other but, rather, are positioned adjacent to each other such that one portion can be folded over to contact the other.
In the above-described devices, the need to manually assemble or manipulate the separate system portions inhibits the occurrence of inadvertent hydration of the hydratable solution-holding component. Nevertheless, separate, or foldable, portions are more costly and cumbersome to use than a unitary device. Such devices also depend on proper assembly by the user and the correct sequence of manipulations of the portions to ensure the hydrating liquid is properly released into the hydratable portion.
Bioelectrode system embodiments disclosed by Gyory include a hydrating liquid-storage component which is separated from a hydratable solution-holding component by a liquid-impermeable sheet. Certain embodiments rely on packaging means to protect from inadvertent release of the hydrating liquid and to cause "automatic" hydration upon removal of the device from the package. The packaging means which effect "automatic" hydration include compression means to rupture or burst the liquid-impermeable sheet; a blade to puncture the liquid-impermeable sheet; and a pull-tab to rip or tear the liquid-impermeable sheet. An alternative embodiment attaches the pull-tab for ripping or tearing the liquid impermeable sheet to a release liner covering a skin contacting surface of the device. In this embodiment, removal of the release liner prior to placement on the patient "automatically" pulls the pull-tab means to rip or tear the liquid-impermeable sheet and thereby release the hydrating liquid. Like Haak, Gyory also discloses liquid flow control means for directing the flow of hydrating liquid through the breached liquid-impermeable sheet to the hydratable solution-holding component.
It can be seen that, in Gyory's devices, it is the liquid-impermeable sheet separating the hydrating liquid-storage component from the hydratable solution-holding component which is physically ruptured, punctured, or ripped. The material comprising the hydrating liquid-storage component, however, remains intact. After the liquid-impermeable sheet is breached and the hydrating liquid is released, the material which formed the now-depleted hydrating liquid-storage component remains positioned within the device. In the case of a ruptured or punctured sheet, all of the now-breached liquid-impermeable sheet material also remains entirely within the device. In the pull-tab embodiment, some of the sheet material is ripped or torn away and is removed from within the device with the attached pull-tab. Nevertheless, in all cases, a substantial portion of the liquid-impermeable sheet material as well as the material comprising the depleted hydrating liquid-storage component remains within the device following the hydration process.
The rupturing, puncturing, or tearing of the liquid-impermeable sheet material exposes torn edges and, thus, inner layers, of the liquid-impermeable sheet including, for example, foil edges. The hydrating liquid-storage component material and the breached liquid-impermeable sheet material, including exposed torn inner layer edges, remain within the device. These no-longer needed materials could interfere with electrical current distribution. These materials also maintain fluid communication with the now-hydrated solution-holding component such that deleterious interaction with the solution is possible. For example, over long-term iontophoresis, i.e. many hours, materials such as exposed foil edges could corrode. Both Haak and Gyory provide liquid-conveying pathways to distribute the hydrating liquid. Such liquid-conveying pathways, however, necessarily affect the transfer of the hydrating fluid because the rate and amount of fluid transferred is limited by the pathway configuration.
It would be an advancement to provide methods and apparatus for isolating a hydrating liquid and for rapidly and thoroughly releasing the hydrating liquid when desired. It would be advantageous to provide such methods and apparatus which are simple and reliable. It would be a further advantage to provide such methods and apparatus which are self-contained and can be produced in a cost-effective and efficient manner and which can easily be subsequently associated with an apparatus to be hydrated when desired.